section10_ak - MIT Department of Biology 7.014 Introductory...

MIT Department of Biology 7.014 Introductory Biology, Spring 2005 Recitation Section 10 Answer Key March 9-10, 2005 Bacterial Genetics—Mutant Hunt A. Introduction to Mutagenesis 1. What does it mean in biological terms to be a mutant? Textbook definition: An individual is a mutant if they carry a change in their hereditary material. Usually for us to be able to identify a mutant it must possess a trait that distinguishes it from what is considered normal. 2. How do you generate a mutant? Does it matter if the organism is unicellular or multicellular? You generate a mutant by making a mutation in the genetic material of the organism which is composed of DNA. In both uni- and mulit-cellular organisms, not every change in genetic material affects a trait of that organism. Any mutation you generate in unicellular organisms will be passed on to its progeny. In multicellular organisms, one mutant cell may or may not cause the organisms to display the changed trait, and will not be passed onto the offspring unless the mutation is in a germ cell (one that makes eggs or sperm). 3. Why would UV irradiation generate mutants? UV light is very high energy and can cause chemical reactions that damage DNA. This damage can cause mutations that are then carried by mutants. 4. Why should you wear sunscreen? Sunscreen blocks and/or absorbs UV light. This prevents UV light from reaching the DNA in your skin cells. If the UV light did reach it might damage the DNA and cause mutations. These mutations could lead to problems with your skin cells in the short term such as killing them (like when you peel after a sunburn) or in the longer term such as causing cancer.

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